[TenTec] Paragon II Failure to Transmit

[Rick - DJ0IP / NJ0IP]

Pete,

The Sherwood presentations were addressing radios in General and are
completely accurate.
Your statement about the 20 kHz roofing filter compromising close in
performance is in general a true statement, but not applicable to the Omni
VII.  I don't blame you for being skeptical, we all were at first.

Rob did not address the OM7 in those first few slides.
The OM7's close in performance is much better than most other radios with
upward conversion, and there is a reason for this.

In fact, Ten-Tec went as far as to call the 455 KHz filters "distributed
roofing filters", even though they are farther downstream.
Whereas the initial 20 kHz filter is indeed a classical roofing filter,
Ten-Tec did not rely on it for the downstream protection.
This is a function of the distributed roofing filters.
We all kind of chuckled when we first heard Ten-Tec use the term, but as I
said earlier, the results speak for themselves.
The up-front gain was kept very low until after the signal passes through
the mechanical filters.
The close-in performance with the mechanical filters is very good, without
them it is a lot worse.
Indeed they contribute to close-in performance.

The technique used was explained to me personally by one of the lead
engineers who designed the radio, but that was about 7 years ago. If you
really want nitty gritty details, you can ask Ten-Tec to explain to you
exactly what they did, but in general it is as I explained above.

73
Rick, DJ0IP

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Peter
Bertini
Sent: Monday, January 21, 2013 10:29 PM
To: tentec at contesting.com
Subject: Re: [TenTec] Paragon II Failure to Transmit

Gary, I am not sure what you are seeing in that presentation, but the first
few slides clearly show that the roofing filter selectivity is what
determines the receiver's close in dynamic range. A 20 kHz roofing filter at
the first IF compromises close in performance. If Sherwood claims otherwise,
he is mistaken :)

Pete
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